JP3064574B2 - Working oil amount switching control device for hydraulic excavator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention sometimes employs a hydraulic breaker or the like as an attachment in place of a bucket normally mounted as a working machine of a hydraulic excavator to perform a work of crushing a structure, a block or the like. Especially in the case of breaker work that requires less oil volume than normal drilling work,
By setting the breaker mode, load sensing control of the hydraulic pump is performed and the optimal oil amount is set.
The present invention relates to a working oil amount switching control device for a hydraulic excavator, wherein an engine for driving a hydraulic pump is driven at a rotation speed at which fuel consumption is reduced.

[0002]

2. Description of the Related Art There is a case where a hydraulic breaker or the like is mounted as an attachment instead of a bucket normally mounted as a working machine of a conventionally used hydraulic excavator to perform a work of crushing a structure, a block or the like. However, in the breaker operation, the oil amount close to half of the excavation operation is sufficient, and therefore, as shown in the absorption torque diagram of the hydraulic pump shown in FIG.
rev) is constant (the absorption torque T of the hydraulic pump is represented by T = kP × V where k is a proportional constant and P is the load pressure. Therefore, for a constant load pressure P0, the absorption torque T0 of the hydraulic pump = Constant), the engine speed for driving the hydraulic pump is controlled as N1, N2, N3 (rev / min) to control the amount of oil required for the breaker work, that is, VN1, VN2,
V · N3 (cc / min) was controlled.

Also, as shown in FIG. 6, a merge switching circuit for two hydraulic pumps is provided, and one of two service valves is switched to switch the flow rate of one pump.fwdarw. And the amount of oil required for each of the breaker operations. In FIG. 6, five switching valves for driving the actuators for turning, boom Hi, service arm Lo, and left running are connected in parallel to a variable displacement hydraulic pump (hereinafter referred to as a main pump) 31, respectively. The main pump 32 is connected in parallel with five switching valves for driving actuators for right traveling, bucket, boom Lo, arm Hi, and service. The two pipes 34 and 35 connected to the outlet port of the service valve 33 shown in FIG. 6 are connected to hydraulic circuits from the service valve 36 on the left side to an actuator 37 such as a breaker, so that they join. A pedal 38 for operating an attachment such as a breaker abuts a pilot pressure control valve (hereinafter, referred to as a PPC valve) 39,
The control pump 40 is used as a hydraulic pressure source. The PP
One of the two pilot circuits 41 and 42 coming out of the C valve 39 is connected to the left end of the service valve 36, and the other is connected to the right end. The pilot circuit 4
1 and 42 are provided with branch circuits 43 and 44, respectively.
The service valve 33 is connected to the right end and the left end via pilot circuit switching valves 45 and 46 each having a solenoid. The solenoids of the pilot circuit switching valves 45 and 46 are connected to a switching switch 50, respectively.

[0004] During normal excavation work or the like, the actuator 37
When the switch 50 is operated to the ON side when the flow rate for two pumps is required, the pilot circuit switching valve 45 is required.
The 46 solenoids are excited and the pilot circuit 41
By operating the pedal 38, the pilot pressure acts on the left end of the service valve 36 and the right end of the service valve 33.
And the left end of the service valve 33.
Thus, the total flow rate of the main pumps 31 and 32 acts on the actuator 37 that drives the attachment. When the hydraulic breaker work is performed by the actuator 37, only the flow rate for one pump is required, so the changeover switch 46 is operated to the OFF side. As a result, the solenoids of the pilot circuit switching valves 45 and 46 are demagnetized,
The branch circuits 43 and 44 of the pilot circuits 41 and 42 are closed, and the pilot pressure acts only on the left end or the right end of the service valve 36 by operating the attachment pedal 38. Thus, only the flow rate of the main pump 1 acts on the actuator 37 that drives the hydraulic breaker.
In addition, the main pump discharge amount is controlled in accordance with the movement of each switching valve spool, and in particular, the main pump discharge amount is controlled to a minimum when each switching valve is in the neutral position, so that the main pump discharge amount is reduced. A relief valve 47 and an orifice 48 are provided in the circuit, and these and the flow rate adjusting mechanism 49 of the main pump 32 are connected by a circuit to control the discharge amount of the main pump.

[0005]

However, in the method of controlling the engine speed as shown in FIG. 5 to reduce the amount of oil necessary for the breaker work and the fuel efficiency of the engine, a predetermined load pressure P0, that is, Hydraulic pump absorption torque T
For 0, reduce the engine speed so that the points A1, A2, and A3 are reached, and reduce the discharge amount of the hydraulic pump so that the oil amount required for the work is reduced. However, the points A1, A2, and A3 move outward from the center of the iso-fuel efficiency diagram (center is 100%) shown by B, and the fuel efficiency of the engine is reduced. It was difficult to plan.

The flow rate switching circuit shown in FIG. 6 has the following problems. (1) Two pilot circuit switching valves 4 in the pilot circuit
5.46 must be provided and the service valve 33
Requires two pipes 34 and 35 to join the main circuit of the attachment actuator 37. This complicates the hydraulic circuit, reduces the reliability of the hydraulic excavator, increases the number of inspection and maintenance steps, and increases the manufacturing cost. (2) Since the amount of oil supplied to the attachment actuator is two-stage switching of one pump or two pumps,
The flow rate cannot be finely adjusted. The present invention focuses on the above-mentioned conventional problems, and in a breaker operation or the like performed with a small amount of oil compared to a normal excavation operation, load sensing control of the hydraulic pump is performed by setting a breaker mode to optimize an oil amount. And an engine for driving the hydraulic pump is driven at a rotation speed at which fuel consumption is reduced.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems in the prior art. Claim 1 is a variable displacement hydraulic pump, an engine for driving the hydraulic pump, and a hydraulic pump. An actuator driven by a pump, an operation valve interposed in a pipeline between the hydraulic pump and the actuator, a load sensing control device of the hydraulic pump, a capacity sensor of the hydraulic pump, a rotation speed sensor of the engine, It comprises a hydraulic sensor of the actuator and a work mode switching device, and inputs signals of the displacement sensor, the engine speed sensor, and the actuating oil pressure sensor, and the engine is operated at a predetermined horsepower designated by the work mode switching device. A control signal operated with minimum fuel consumption is calculated, and the load sensing control device and the engine gas The load sensing control device of the variable displacement hydraulic pump according to claim 1 is provided with a controller for driving the displacement control device of the hydraulic pump and a pipe between the hydraulic pump and the actuator. With the hydraulic pressure upstream and downstream of the intervening operation valve as pilot pressure, the pressure difference between the pilot pressures increases,
The control signal for operating the engine with minimum fuel consumption according to claim 1 is a load sensing valve that acts to reduce the capacity of the hydraulic pump by increasing the control signal from the controller. It was configured to be set by torque and engine speed.

[0008]

According to the above construction, the following operation is performed. When a hydraulic excavator drives an actuator that requires a relatively small flow rate of oil such as a breaker, the operation valve is operated by a separately provided operation lever. Thus, the displacement of the variable displacement hydraulic pump is controlled. When a control signal is input to a controller from a displacement sensor of a hydraulic pump, a rotation speed sensor of an engine, a hydraulic sensor of an actuator, and a work mode switching device, a predetermined value designated by the work mode switching device in the controller is provided. A control signal for operating the engine with minimum fuel consumption at horsepower is calculated, and the control signal is output to the load sensing capacity control device and a governor driving device of the engine. Therefore, in a normal excavation operation, when the engine is set to be driven with the minimum fuel consumption, even if the operation mode is switched to a work mode that requires a relatively small amount of oil, such as a breaker operation, the engine has the minimum power at the horsepower. The motor is driven at a rotational speed that is fuel-efficient. In addition, the load sensing control device of the hydraulic pump uses load pressure upstream and downstream of the operation valve as a pilot pressure, and when the pressure difference between the pilot pressures increases and the control signal from the controller increases, the load sensing A control pressure is supplied to the drive cylinder of the displacement control device of the hydraulic pump by a valve to reduce the displacement of the hydraulic pump. Further, the control signal for operating the engine with the minimum fuel consumption is set based on the engine torque and the engine rotation speed that provide the minimum fuel consumption on a horsepower curve such as an engine.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 is a diagram showing an embodiment of a control circuit according to the present invention, FIG. 2 is a diagram showing details of a controller in FIG. 1, FIG. 3 is a diagram showing an equal horsepower curve of an engine, and FIG.
Is the hydraulic pressure of the hydraulic pump driven by the engine.
It is a figure showing a capacity curve. In FIG. 1, 1 is an engine, 2 is a hydraulic pump driven by the engine 1,
3 is a breaker, 4 is a breaker operating valve interposed in the pipelines 5, 11 connecting the hydraulic pump 2 and the breaker motor 3, 6 is a breaker operating lever for operating the breaker operating valve 4, and 7 is the breaker operating lever. A displacement control cylinder 8 for driving the swash plate 2a of the hydraulic pump 2;
9 is a load sensing valve for switching the control pressure of the cylinder, 9 is a control pump as a control pressure valve of the capacity control cylinder 7,
Reference numeral 0 denotes a hydraulic pressure sensor for converting the hydraulic pressure at the downstream side 11 of the operation valve 4 into an electric signal, 12 denotes a work mode changeover switch of the hydraulic excavator, S denotes an excavation mode button, B denotes a breaker mode button, and 13 denotes a hydraulic pump. 2, a pump displacement sensor for detecting the displacement of the engine 2, 14 an engine revolution sensor for detecting the revolution speed of the engine 1, 15 a hydraulic sensor 10 for the actuator 3, a work mode changeover switch 12, and a pump displacement sensor 13 for the hydraulic pump 2. And a detection signal and a command signal from the engine speed sensor 14 of the engine 1, and control signals iN and iV for operating the engine 1 with the minimum fuel consumption at a predetermined horsepower designated by the work mode changeover switch 12 are calculated. Thus, the control signal iN is sent to the governor driving device 1a of the engine 1, and the control signal iV is sent to the source of the load sensing valve 8. A controller that outputs to the solenoid 8a, 8b is a pilot cylinder of the load sensing valve 8 connected to the upstream pipe 5 of the operation valve 4, and 8c is a pilot cylinder of the load sensing valve 8 connected to the downstream pipe 11 of the operation valve 4. A pilot cylinder, 8d is a differential pressure setting spring of the load sensing valve 8, 7a is provided in the bottom chamber 7b of the displacement control cylinder 7, and urges the piston 7d in the direction of the rod chamber 7c. A piston rod 16 is connected to the hydraulic oil tank 16.
17 to 24 will be described in detail with reference to FIG. Also, 25
Is a power supply, 26 is a magnet, 27 is a changeover switch, 27
a is a spring, 28 is a hold switch, and 28a is a spring.

In FIG. 2, reference numeral 1a denotes a cabana driving device;
a is a solenoid of the load sensing valve 8, 15 is a controller, the controller 15 is a target value setter 17 for setting a target engine speed NS and a target engine torque TS for the excavation mode, a target value setter 17 for setting the target engine torque TS and the hydraulic pressure. A capacity difference calculator 19 for calculating a difference ΔVS between a target capacity VS calculated from a detection value P of the sensor 10 and a detection value V of the capacity sensor 13, and a target engine speed NS and an engine speed sensor 14; An engine speed difference calculator 20 for calculating a difference ΔNS from the detected actual engine speed N, and a set engine speed NB and a set engine torque TB for the breaker mode are similarly set for the breaker mode. And a target capacity VB calculated from the target engine torque TB and the detection value P of the oil pressure sensor 10. A capacity difference calculator 21 for calculating a difference ΔVB between the detected value V of the sensor 13 and a difference ΔNB between the target engine speed NB and the actual engine speed N detected by the engine speed sensor 14 And a control signal generator 23 for converting the displacement difference signal ΔVS or ΔVB into a control signal iV applied to the solenoid 8a.
A control signal generator 24 for converting the engine speed difference signal .DELTA.NS or .DELTA.NB into a control signal iN applied to the governor drive 1a.

FIG. 3 is a diagram showing an equal horsepower and an equal fuel consumption curve drawn on an engine torque-rotation speed graph, where A is an equal fuel consumption curve, and the center indicates 100% fuel efficiency. Also HP
S is the horsepower curve in the excavation mode, and HPB is the isopower curve in the breaker mode. FIG. 4 is a diagram showing an iso-torque curve drawn on a hydraulic-capacity graph of a hydraulic pump driven by the engine, where TS is the hydraulic pump absorption torque of the engine torque TS in the excavation mode of FIG.
Is the hydraulic pump absorption torque of the engine torque TB in the breaker mode of FIG.

Next, the operation of the configuration shown in FIGS. 1 and 2 will be described. When the hydraulic excavator is to be operated in the normal excavation mode, when the excavation mode button S of the mode changeover switch 12 is pressed, the magnet 26 is demagnetized because the voltage of the power supply 25 is not applied to the magnet 26 and the switch 27 is depressed. Is connected to the contact A by a spring 27a. Accordingly, the target engine speed NS and the target engine torque TS are set by the target setting device 17 in the controller 15, and the target engine torque TS and the oil pressure sensor 10 are set.
Is input to the capacitance difference calculator 19. As is well known, since TS = kPVS... K can be expressed as a proportionality constant, the target pump displacement VS is calculated, and the difference ΔVS between the target pump displacement VS and the detection value V of the pump displacement sensor 13 is calculated. Is done. When the capacity difference ΔVS signal is output to the control signal generator 23, a control signal iV corresponding to the capacity difference signal ΔVS as shown is output to the solenoid 8a of the load sensing valve 8. Since the control signal iV is set to a large value when the displacement signal .DELTA.VS is small in the control signal generator 23, for example, the pump displacement sensor 1 is set with respect to the target pump displacement VS.
If the actual pump displacement V detected at 3 is too large, the displacement difference signal ΔVS becomes small and the control signal iV becomes large, so that the urging force of the solenoid 8a pushing the load sensing valve 8 to the right increases. Therefore, the control pressure of the control pump 9 is supplied to the bottom chamber 7b of the displacement control cylinder 7, so that the piston rod 7e of the displacement control cylinder 7 moves to the left to reduce the displacement of the swash plate 2a of the variable displacement hydraulic pump 2. Control in the direction you want. In this way, control is performed so that the displacement difference signal ΔVS is 0, that is, the actual pump displacement V becomes the target pump displacement VS.

Similarly, the target engine speed NS set by the target value setting device 17 and the actual engine speed N detected by the engine speed sensor 14 are input to the engine speed difference calculator 20. Then, a difference .DELTA.NS between the target engine speed NS and the actual engine speed N detected by the engine speed sensor 14 is calculated.
Since the control signal iN is set to a small value when the engine speed difference signal .DELTA.NS is small in the control signal generator 24, for example, the target engine speed NS
On the other hand, if the actual engine speed N detected by the engine speed sensor 14 is too small, the engine speed difference signal ΔNS increases and the control signal iN also increases. A large number of injections are performed to increase the engine speed N to increase the engine speed difference signal ΔN
S is controlled to be 0, that is, the actual engine speed N is equal to the target engine speed NS, and the digging operation can be performed with the target engine speed NS and the target engine torque TS that are the minimum fuel consumption. When working in the breaker mode in which almost 50% of the working oil amount is used for the normal excavation work, when the breaker mode button B of the mode changeover switch 12 is pressed, the voltage of the power supply 25 is applied to the magnet 26. Since the voltage is applied, the changeover switch 27 is
7a, the hold switch 28 is connected to the contact C
The breaker mode is maintained by the hold switch 28 even when the hand that presses the breaker mode button B is released, and the power supply voltage is supplied to the target setting device 18 in the controller 15. Therefore, the target engine speed NB and the target engine torque TB are set by the target value setting device 18, and the breaker work is performed by the target engine speed NB and the target engine torque TB which minimize the fuel consumption in the same manner as in the normal excavation mode. can do.

[0014]

As described in detail above, according to the present invention, the following effects can be obtained. (1) The change of the working oil amount by changing the work mode can be easily performed by the mode changeover switch. (2) A plurality of work modes are made possible by switching the work mode, but work can be performed with minimum fuel consumption in any of the work modes. (3) Since the operation valve can be controlled in a wide operation range, the operability of the operator can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a control circuit according to the present invention.

FIG. 2 is a diagram showing details of a controller in FIG. 1;

FIG. 3 is a diagram showing torque and rotation speed on an equal horsepower curve of an engine.

FIG. 4 is a diagram showing a hydraulic pressure-capacity curve of a hydraulic pump driven by the engine.

FIG. 5 is a diagram showing adjustment of an oil amount of a hydraulic pump by rotation of an engine in a conventional technique.

FIG. 6 is a diagram showing oil amount adjustment by a merging switching circuit of a plurality of hydraulic pumps in the related art.

[Explanation of symbols]

 Reference Signs List 1 engine 1a governor driving device 2 variable displacement hydraulic pump 2a swash plate 3 breaker 4 breaker operating valve 5 upstream pipeline 6 breaker operating lever 7 capacity control cylinder 7a spring 7b bottom chamber 7c rod chamber 7e piston rod 8 load sensing valve 8a solenoid 8b Pilot cylinder 8c Pilot cylinder 8d Differential pressure setting spring 9 Control pump 10 Hydraulic sensor 11 Downstream line 12 Mode switch 13 Pump displacement sensor 14 Engine speed sensor 15 Controller 16 Tank 17, 18 Target value setting device 19, 21 Pump displacement Difference calculator 20,22 Engine speed difference calculator 23,24 Control signal generator

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) E02F 9/22

Claims (3)

(57) [Claims] 1. A variable displacement pump, an engine for driving the hydraulic pump, an actuator driven by the hydraulic pump, an operation valve interposed in a pipe between the hydraulic pump and the actuator, A load sensing control device, a capacity sensor of the hydraulic pump,
The engine includes a speed sensor of the engine, a hydraulic pressure sensor of the actuator, and a work mode switching device. The signals of the displacement sensor, the rotation speed sensor of the engine, and the hydraulic pressure sensor of the actuator are input and designated by the work mode switching device. A control signal for operating the engine with minimum fuel consumption at a given predetermined horsepower, and comprising a controller for outputting the load sensing control device and a governor drive device of the engine to a hydraulic excavator. Switching control device. 2. The load sensing control device of a variable displacement hydraulic pump according to claim 1, wherein the displacement control device drive cylinder of the hydraulic pump and the hydraulic pressure upstream and downstream of an operation valve interposed in a pipeline between the hydraulic pump and the actuator. A hydraulic pressure excavator, wherein a pressure difference between the pilot pressure increases and a load sensing valve that acts to reduce the capacity of the hydraulic pump by increasing a control signal from the controller. Control device for switching the amount of working oil in the machine. 3. The hydraulic excavator according to claim 1, wherein the control signal for operating the engine with the minimum fuel consumption is set based on the engine torque and the engine speed, which is the minimum fuel consumption on the horsepower curve of the engine or the like. Work oil amount switching control device.